Bitter medicines, foods which are apt to change their shape with temperature rise, etc. have been supplied after forming a coating layer with a sugar coating composition so as to be taken or eaten with ease.
Most of the conventional sugar coating compositions consist mainly of sugar, a binder, and water. Improvements have been added to these compositions in taste and adhesion to the center core to be coated which contains a medicine or a food material (hereinafter inclusively referred to as a "center").
As the binder used in the conventional sugar coating compositions to enhance adhesion of the coating layer to the center, gelatinizers such as gelatin and agar and gums such as gum arabic, xanthane gum, and guar gum have been widely used. For example, JP-A-62-5910 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a sugar coating composition containing hydroxypropylmethylcellulose and a water-soluble cellulose derivative as binders and sucrose, and JP-A-2-138117 discloses a sugar intermediate coating layer comprising hydroxypropylmethylcellulose and mannitol.
Although gelatin has satisfactory binding properties, sugar-coated tablets prepared by using gelatin undergo reduction in disintegrability and also browning of color with the passage of time.
While excellent in extending properties, gum arabic has insufficient binding properties. If used in an increased amount, the texture becomes rough when dried.
Water-soluble cellulose as a binder, when coated on a center to form sugar-coated tablets, provides a smooth texture. However, water-soluble cellulose itself is unpleasant to the taste and has been limited in use.
Further, there is a problem that the viscosity of the sugar coating composition prepared by using these conventional binders increases when it is applied to a center, making the coating operation difficult. In addition, the multi-layered structure in order to achieve good adhesiveness of the sugar coating layer and good texture results in too large sugar-coated preparations.